Low emission coatings have been applied on windows to limit the transmission of IR (heat) through the windows. These coatings are very widespread; however they are characterized by fixed transmission characteristics. For optimal energy efficiency, windows should allow the transmission of IR in the winter so it contributes to heating the building, and block it in the summer to help the building stay cool. The amount of visible light should also be tuned to optimise the comfort of ambient conditions to users and minimize the amount of general lighting needed.
Smart windows, in which the light transmission through the window can be controlled, have been developed using electrochromic layers, liquid crystals and suspended particles. Automated blinds systems located between two glass panes or inside buildings have also been developed.
Current technology for smart windows, which is mainly based on the use of electrochromic layers, has severe limitations in terms of lifetime, speed, maximum IR transmission and visual aspect. Macroblinds have also very severe drawbacks such as cost, reliability and visual appearance.
Rolling electrodes have been employed in telecommunications applications as, for example, light modulators. Such devices typically have small dimensions, in the order of 1 mm to 1 cm.